Preparation of cellulose fiber for conversion into derivatives



- 1931- G. A. RICHTER ET AL 1,826,825

PREPARATION OF CELLULOSE FIBER FOR CONVERSION INTO DERIVATIVES Filed Oct. 27, 1927 Oct. 13, 1931. G. A. RICHTER ET AL PREPARATION OF CELLULOSE FIBER FOR CONVERSION INTO DERIVATIVES Filed Oct. 27, 1927 2 Sheets-Sheet 2 Patented Oct. 13, 1931 PATENT OFFICE UNITED STATES GEORGE A. nrcnrm, mwron scnun, AND ROYAL. a. mason, or BERLIN, New HAMPSHIRE, assronons To nown COMPANY, or BERLIN, NEW namrsmana CORPORATION OF MAINE PREPARATION OF CELLOLOSE'IIBEB FOR CONVERSION DERIVATIVES Application flled october 27, 1927 Serial No. 229,086.

This invention relates to the preparation of cellulose fiber for conversion into'cellulose derivatives, its object being to makeypossible the realization of optimum results upon such conversion. I f

In preparing cellulose fiber for conversion into cellulose derivatives, e. g2,v cellulose n1- trates, it has heretofore sometimes'been the practice to sheet the fiber into paper and then m' to shred or tear the sheet into small squares or short rectangular pieces, i'ntopieces of random shapes and dimensions, or into exceedingly minute shred-sol particles presenting almost as much edge as surface. We

15' have discovered that shape and dimension have a marked influence upon the results obtained upon conversion, and that-v to secure optimum results it is necessary to usenarrow strips or streamers, rather than small squares 20' or short rectangular pieces, p ieces of random shapes and dimensions, or minute shreds or particles. 1 v

While not restricted thereto, our discovery may be applied to great advantage in the 25 production of nitro-cellulosesffor we have found that by using paper strips or streamers, we gain in yield and quality of product and at the same time reduce acidretention. We also increase the facility of handling, and

so arev able to use paper of a thickness 'orbasis Weight considerably greater than that'ordinarily used, without running into difficulty.

In research work performed in connection with our discovery, it has been our experience that with shreds under, say," in-"width there is apt to be disintegration in the'acid bath and loss of nitrated material through the holes in the centrifuge'basket, leading to low yields and an inferior product On the other hand, pieces wider than, say, about %"-for instance, pieces of an average size of 1 x "Ytend to stick together in the acid bath and in the centrifuge, thereby being reacted upon non-uniformly and causing more or less hydrolysis when'the centrifuged material is drowned in'w ateras the first step in washing the nitratedmaterial free from acids. The yield is thereby 'l.owered,"as*are also the strength and viscosity of the nitrocellulose. This is particularly true when the in the acid bath is avoided, and the ribbons of paper interlace or felt together in the centrifuge, thereby reducing the fiber loss through the holes in the centrifuge basket to an insignificant value. The interlaced ribbons separate readily when drowned, perhaps because of the fact that strips of the size described are somewhat springy and tend to curl. The final result is a maximum yield of strong, well-nitrated product even when the basis weight of the paper has been increased to, say, 20 to 22 pounds. The ribbons are easily handled with pitchforks and rakes before and after nitration, and are preferable to cotton linters, in that they are free from dust and give more uniform results because of their more uniform physical condition.

Our invention may best be appreciated bv citing specific examples. The raw material employed in these examples was a waterleaf paper prepared from a high alpha cellulose wood fiber, but it is to be understood thatthe results are illustrative of what takes place in greater or less degree when cellulose fiber of other origin is employed. Preferably, the fiber is beaten to a material extent, as described in our application, Serial No. 97,998,

filed March 27, 1926, prior to sheeting into paper 3 long and wide, when similarly treated resulted in 150% to 152% yield of nitrated product and an acid retention of 4.3. Solutions prepared from the nitrated strips were of greater clarity than solutions prepared from the nitrated squares.

narrow strips atthe paper mill, while continuousl coming oif the paper machine or a rewin er, and marketed in baled form, or it may be cut to form a continuous series of rows of suchstrips integral with the bod of the sheet, and then wound up into rolls, w ich are less bulky and easier to handle than strips.

The rolls may then be shipped to derivative mills, where they may be unwound and the strips progressively severed from the sheet, as by passing through a coarse, simple shred- Our method may best be understood by the following more detailed description thereof when considered in connection with the accompanying drawings, wherein Figure 1 illustrates diagrammatically and conventionally means for cutting the sheet for rolling.

Figures 2, 3, and 4: each show a portion of the sheet cut for-rolling.

Figure 5 shows in perspective 2. rolled sheet of paper out into strips integral with the body of the sheet. a

Figure 6 illustrates diagrammatically and conventionally means for severing the strips from the sheet. c

Figure 7 illustrates somewhat difierent means for this purpose.

Figure 8 shows in perspective a severed strip.

Referring to Figure 1 of the drawings, 1

represents a continuous sheet of paper coma ing directly from a paper machine or a repair of guide rolls 2 and thence between a rotary cutter 3 and a supporting roll 4, as shown the sheet being drawn along by a pair of feed rolls 5 and finally being wound into a roll 6. The cutter 3 is designed tot form a series of rows of longitudinal, shar ly cut strips integral with the sheet, this belng effected by producing a series of transverse rows of parallel, longitudinal slits 7 in the sheet. The slits may be of any suitable length, say 1" to 12", and spaced adistance in magnitude of the order of to The slits shown in Figure 2 are arranged in staggered relation transversely of the sheet, with the ends of the slits of one row somewhat overrunning the ends of the slits of an adjacent row, so that by cutting across the successive. zones of overrun, a mass of individual strips is at once produced. If the strips are to be severed from the sheet as by a coarse, simple shredaaaaees Any one of these ways of cutting the longitudinal slits permits winding of the sheet into a roll such as illustrated in Figure 5.

Inlieu of winding into rolls after longitudinally slitting, as shown in Figure'5, the sheet cutas illustrated in Figure 2 may pass directly from the rolls 5 under a rotary cutter 8 designed to cut the sheet transversely across the successive zones of overrun, thus at once producing a mass of individual strips, which may be allowed to fall into a suitable receptacle 9. Or, as shown in Figure 6, the sheet ma pass from the feed rolls 5 between apair 0 rolls 10 rotating at suitably higher speed than the rolls 5, and thus serving to tear the strips from the body of the paper where the slits overrun. The preparatlon of strips may thus be carried out continuously, beginning with pulp, continuing through the formation of a waterleaf sheet of paper on a paper machine, and ending with cutting of the paper into a mass of individual strips as the sheet comes off the paper machine.

Itis to be understood that in lieu of forming straight-lined slits in the paper to produce narrow strips having straight side edges, we may form zig-zag or sinuous slits spaced so as to yield narrow strips upon coarse shredding. Moreover, the'slits may be of varying lengths, from, say, 2" to 12", in order to obtain a mass of strips of difl'erent lengths, which may interlace even better during baling, centrifuging, etc., than strips of give a mass of the desired characteristics. It

is to be further understood that. while we find it preferable to cut the strips lengthwise of the sheet or along the machine direction as hereinbefore described, the stripsmay be cut transversely of the sheet or across the machine direction.

Our discovery that long, narrow strips as hereinbefore described yield excellent results even when the basis weight of the sheet is raised from the usual 10 to 12 pounds to 20 to 22 pounds is of considerable importance, for, on. the one hand, the preparation of the heavier paper is much less expensive and, on the other hand, the heavier sheet is less bulky, increasing materially the weight of cellulose that can be handled per nitrating pot.

While the specific examples herein given are directed to the preparation of cellulose nitrates, our invention may be applied to advantage when preparing other derivatives such as cellulose acetates, for here, too, han-. dling before and after acetylation is facili tated, and there is no tendency for the strips to pack together or disintegrate during acetylation or centrifuging.

Having thus described certain embodiments of this invention, it should be evidentto those skilled in the art that various changes and modifications might be made therein without departing from the spirit or scope of invention as defined in the appended claims.

What we claim is:

1. Material for conversion into cellulose derivatives, comprising a mass of strips of waterleaf paper having a width of the order of magnitude of to and having a length of at least about 1" to 12".

2. Material for conversion into cellulose derivatives, comprising amass of narrow waterleaf paper strips of beaten fiber having a length of at least about 1" to 12". 3. Material for conversion into cellulose derivatives, comprising a mass of narrow waterlcaf paper strips of mercerized fiber.

4. Material for conversion into cellulose derivatives, comprising amass of narrow waterleaf paper strips of beaten and mercerized fiber. a 5

5. Material for conversion into cellulose derivatives, comprising a mass of narrow strips of waterleaf paper of difi'erent lengths but falling within the range of at least about 1" to 12".

6. Material for conversion into cellulose derivatives, comprising a mass of narrow strips of waterleaf paper having a basis weight greater than 12 pounds.

7. A step product in the preparation of material for conversion into cellulose derivatives, consisting of a rolled sheet of waterleaf paper having a series of transverse rows of longitudinal slits therein.

8. A step product in the preparation of material for conversion into cellulose deriva-- tives, consisting of a sheet of waterleaf paper having a series of transverse rows of parallel longitudinal slits therein.

9. A step product in the preparation of material for conversion into cellulose deriva-' cellulose fiber to a material extent, sheeting the beaten fiber into paper, mercerizing the paper, cutting the paper into narrow strips, and converting t 0 strips into cellulose derivatives. 7

13. A method which comprises cutting up paper into narrow strips having a length of at least about 1" to 12" and converting the strips into cellulose derivatives.

14. A method which comprises nitratingnarrow paper strips having a length 0 about 1" to 12".

15. A method which comprises nitrating narrow strips of waterleaf paper having a width of an order of magnitude of about 1/16" to and having a length of at least about 1" to 12".

16. A method of preparing cellulose fiber for conversion into cellulose derivatives, which comprises sheeting such fiber on a paper machine and sharply cutting a continuous series of transverse rows of longi- 'tudinal slits-in the paper sheet while it is coming off the machine.

17. A method of preparing paper for conversion into cellulose derivatives, which comprises cuttin a continuous series of transverse rows 0 longitudinal slits in a continuous sheet of paper to form a succession of strips integral with the sheet, and then progressively severing the strips from the sheet. 18. A method of preparing paper for cor.- version into cellulose derivatives, which comprises cutting a continuous series of transverse rows of longitudinal slits in a continuous sheet of paper to form a succession of strips inte ral with the sheet, rolling up the sheet, an then unrolling and progressively severing the strips from the sheet.

'19. A method of preparing paper for conversioninto cellulose derivatives, which comprises sharply cutting a continuous series of transverse rows of longitudinal slits in a continuous sheet of paper to form a succession of strips integral with the sheet, and rolling 105 up the sheet.

20. A method of preparing material for conversion into cellulose derivatives from a continuous sheet of paper, which comprises cutting a continuous series of rows of paralno le] longitudinal slits arranged in staggered relation transversely of the sheet with the ends of the slits of one row somewhat overrunning the ends of the slits of an adjacent row, and cutting across the successive zones 115 of overrun to produce a mass of paper strips.

In testimony whereof we have afiixed our signatures.

GEORGE A. RICHTER.

MILTON O. SCHUR. ROYAL H. RASCH. 

